Storage library systems are often used by enterprises and the like to efficiently store and retrieve data from storage media. In the case of some storage libraries, the media are data cartridges (e.g., tape cartridges) that are typically stored and indexed within a set of magazines. When particular data is requested, a specialized robotic mechanism finds the appropriate cartridge, removes the cartridge from its magazine, and carries the cartridge to a drive that is designed to receive the cartridge and read its contents. Some storage libraries have multiple drives that can operate concurrently to perform input/output (10) operations on multiple cartridges.
To facilitate movement of the robotic mechanism throughout the storage library system, some implementations include one or more carriages (e.g., platforms) that move in one or more axes along one or more guides. For example, the robotic mechanism can be connected to a platform that moves in a Z direction (e.g., up and down with respect to the storage library system) along one or more guide rails. In a non-modular implementation of the storage library system, it is straightforward to minimize any potential discontinuities and/or other undesirable features of a guide. For example, a one-piece guide rail can be installed, multiple pieces can be installed with high levels of tolerance, etc. This can allow the one or more carriages to move along the one or more guides substantially without interference from imperfections in the guides.
In modular implementations of the storage library system, one or more expansion modules can be added to a base module to expand the capacity of the storage library system. Allowing the robotic mechanism to operate within those expansion modules may involve extending the one or more guides into those modules. However, it can be difficult to minimize undesirable guide transitions between modules while allowing expansion modules to be easily installed and uninstalled. For example, designing expansion modules for easy installation may involve designing the expansion modules to have a certain amount of float in one or more directions during installation. This float, however, may not be tolerable at the transition point between the module's guide and the guide of an adjacent module.
Accordingly, it may be desirable to provide guide alignment techniques that allow for float in module installation while maintaining a relatively high level of tolerance in guide transitions.